Conventional laser bar code readers scan a laser beam across a distant bar code label and detect an optical signal reflected off the bar code. However, ambient light, from sources such as low energy lights, neon signs, and sunlight, are also present in the detected signal. The frequency range of the ambient parasitic light is wide, ranging from DC to high frequencies. The ambient light component severely degrades the signal to noise ratio of the reflected bar code signal when the reading distance between the bar code reader and the bar code increases.
Retro reflection systems are well known in the art for extracting a signal from random noise. However, these systems are large, have low scanning frequencies, and are costly. Thus, they are not suited for use in handheld computers or bar code scanners.
There is a need for a system that overcomes the above problems, as well as providing additional benefits. Overall, the above examples of some related systems and associated limitations are intended to be illustrative and not exclusive. Other limitations of existing or prior systems will become apparent to those of skill in the art upon reading the following Detailed Description.